Boron-containing high-strength high-reaming steel and manufacturing method thereof

Abstract

The invention relates to boron-containing high-strength high-reaming steel and a manufacturing method thereof. The boron-containing high-strength high-reaming steel is prepared from the chemical components in percentage by weight: 0.01-0.05% of C, 0.2-0.6% of Si, 0.8-1.5% of Mn, less than or equal to 0.02% of P, less than or equal to 0.005% of S, less than or equal to 0.008% of N, less than 0.001%of Als, less than or equal to 0.0050% of Ca, 0.001-0.006% of B, 0.01-0.08% of Nb, 0.007%-0.020% of total oxygen [O]<T>, and the balance of Fe and other inevitable impurities. Nb, B and other microalloy elements are selectively added into the steel; the alkalinity of slag, the type and melting point of inclusions in steel, the content of free oxygen in molten steel and the content of acid-solublealuminum Als are controlled in the smelting process; then a cast strip is casted through double-roller thin strip continuous casting, directly enters a lower closed chamber with a non-oxidizing atmosphere, and enters an online rolling mill for hot rolling under a closed condition; rolled strip steel is cooled in a gas atomization cooling mode, and a produced steel coil can be directly used as a hot rolled plate and can also be used after being subjected to acid pickling and leveling.

Description

technical field [0001] The invention relates to the manufacturing technology of high-hole-expanding steel, in particular to a boron-containing high-strength high-hole-expanding steel and a manufacturing method thereof. Background technique [0002] Most of the traditional thin strip steel is produced by multi-pass continuous rolling of the slab with a thickness of 70-200mm. The traditional hot rolling process is: continuous casting + slab reheating and heat preservation + rough rolling + finishing rolling + cooling + Coiling, that is, firstly obtain a cast slab with a thickness of about 200mm through continuous casting, reheat the cast slab and keep it warm, then perform rough rolling and finish rolling to obtain a steel strip with a thickness generally greater than 2mm, and finally process the steel strip Laminar cooling and coiling complete the whole hot rolling production process. If it is necessary to produce a steel strip with a thickness of less than 1.5mm (inclusive)...

AI Technical Summary

Problems solved by technology

[0008] With the increasing requirements of automobile design on the chassis structure, the forming of parts is more complex, and the requirements for flanging and hole reaming performance of steel plates are further improved. The strength and rigidity of parts can be improved through the shape design of flanging and local reaming of automobile parts, which can To achieve the purpose of reducing the thickness and weight of automobile steel plates, traditional carbon-manganese solid-solution strengthened steel and low-alloy precipitation-strengthened steel structural steel plates are difficult to meet the forming requirements of automobile chassis and cantilever parts, such as traditional 440MPa steel plate carbon-manganese solid-solution strengthened steel and low-alloy The hole expansion rate of precipitation strengthened steel is only between 50% and 70%, thus the high hole expansion steel was born

In the 1990s, the United States and Japan successively developed hot-rolled steel sheets with high hole expansion performance of 440-780MPa, and the hole expansion rate was 70%-131%. They are mainly used in formability, especially those that require good flanging performance. For automobile chassis, wheels and other parts, the hole expansion performance of the steel plate is related to the composition, strength and structure uniformity of the steel plate. Because it contains more precious alloy elements Cr, Nb, Ti, V and Mo, etc. Ferrite / bainite dual phase structure can be obtained under the same conditions, but its cost is higher

[0020] Chinese patents CN105154769 and CN106119702 respectively disclose a kind of 780MPa and 980MPa grade hot-rolled high-strength high-reaming steel and its manufacturing method, both of which are in the category of high-strength steel. Multi-microalloying elements are used to strengthen the steel type, and the alloy cost is relatively high; at the same time, its production method adopts traditional continuous casting + traditional hot rolling process to produce

[0021] International patent WO200928515 uses C, Si, Mn to add a small amount of Nb, Ti alloy elements, and can produce reaming steel with a tensile strength above 490MPa. Hot rolling must adopt a two-stage laminar flow cooling method, which can be more accurately simulated in the laboratory. However, in hot rolling production, the strip speed changes greatly during hot rolling, and the temperature of the steel plate in the air cooling section cannot be measured. A two-stage cooling model is used to control laminar cooling, and the steel plate The actual temperature fluctuates greatly, which will easily lead to large fluctuations in the performance of the steel coil head, middle and tail

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